Nowadays, bottle blow-molding machines are widely applied to fabrications of various plastic bottles (such as PET bottles). A traditional bottle blow-molding machine comprises various different mechanical parts, such as a structure for opening and closing molds, a structure for feeding material and blowing bottles, a structure for ejecting bottles, a structure for conveying and etc., wherein the structure for opening and closing molds can be designed and driven by selectively using various different power sources (such as motor, pneumatic cylinder, hydraulic cylinder or cam).
For example, Taiwan Utility Model Patent No. M326468 discloses a “Mechanism for Opening and Closing Molds of Bottle Blow-Molding Machine”, wherein a machine base of a bottle blow-molding machine is provided with two opposite mold bases which can horizontally slide back and forth, and each of the mold bases is linked to the machine base through a toggle assembly. Each of the two toggle assemblies is pivotally connected to a first connection rod assembly which is driven by a first cam and a second cam of a cam assembly, respectively. Thus, the two mold bases can be simultaneously driven to be opened or closed. Furthermore, a lower mold base which can longitudinally slide back and forth is linked to a second connection rod assembly which is driven by a third cam of the cam assembly. Thus, the lower mold base can be simultaneously driven to be opened or closed.
However, there are some problems existing in the actual use of the traditional mechanism for opening and closing molds, as follows: during opening or closing the mold bases, a downward push force fed back from the mold bases and connection rods of the first connection rod assemblies will directly abut against each of the cam surfaces on the cam assembly. After the cam surfaces are long-term used and worn, the precision of the first connection rod assemblies for pushing the two mold bases to close will be affected. In other words, when closing the mold bases, a gap may exist between two contact surfaces of the two mold bases, so as to affect the yield of subsequently feeding material and blowing bottles. Moreover, because the downward push force from the connection rods of the first connection rod assemblies during opening the mold bases will directly abut against each of the cam surfaces on the cam assembly, the cam assembly needs a greater rotation power to push the connection rods of the first connection rod assemblies for opening the mold bases. Meanwhile, the excess push loading transmitted through the connection rods may cause the bending of the connection rods or the pivotal vibrations, noise or abrasion on various pivotal points. In addition, for simultaneously driving the two first connection rod assemblies and the second connection rod assembly, the cam assembly must have three types of different cams, and thus the purchase cost of the cam assembly will be increased. Besides, if installation angles between the three cams are changed, the mold opening and closing operations of the two mold bases and the lower mold base will be affected and can not coordinate with each other, resulting in affecting the yield of subsequently feeding material and blowing bottles. Furthermore, the cam assembly belongs to one of components having higher cost, so that the abrasion of the cam assembly will cause higher maintenance and replacement cost.
As a result, it is necessary to provide a multi-rod structure for opening and closing molds to solve the problems existing in the conventional technologies, as described above.